1. Field of the Invention
The present invention relates to a wireless LAN communication system including a wireless LAN terminal apparatus having a wireless LAN (IEEE802. 11a/11g/11b) connection function and a base station apparatus making a wireless connection to the wireless LAN terminal apparatus to connect the terminal apparatus to the network, and more particularly to a wireless LAN connection method for establishing a connection between the wireless LAN terminal apparatus and the base station apparatus.
2. Description of Related Art
In recent years, hot spot services are attracting great attention which provides Internet-access by use of wireless LAN in a specific shop or the like. In addition, wireless LAN requiring no connection cable is also widely diffusing into households.
In such a wireless LAN communication system, in order to connect with the wireless LAN network, firstly the wireless LAN terminal apparatus has to search a connectable base station apparatus (hereinafter, referred to as an AP: Access Point) and wirelessly connect with the AP; as means for searching quickly a connectable AP, the wireless LAN terminal apparatus utilizes active scan. Active scan is an operation of a wireless LAN terminal apparatus searching a wireless LAN network existing around this terminal apparatus by sending a probe request to an AP and receiving a probe response returned from the AP. When the wireless LAN terminal apparatus cannot find any AP to be connected therewith even after performing active scan, an automatic homing operation will be performed in which scanning operation is repeated. However, when the automatic homing operation is performed, radio wave is continuously transmitted from the wireless LAN terminal apparatus, thereby causing a problem of increasing the power consumption of the wireless LAN terminal apparatus.
When used in varied places in the open air or within a household, such as a hot spot service area, wireless LAN terminal apparatuses are usually driven by battery. Accordingly, the operable time of a wireless LAN terminal apparatus is dependent on the capacity of battery. Thus, when automatic homing is performed by the wireless LAN terminal apparatus to increase its power consumption, the operable time is reduced. Consequently, with wireless LAN terminal apparatuses, the reduction of power consumption at the time of the automatic homing operation is desired.
As a technique of reducing the power consumption at the time of waiting in a wireless LAN terminal apparatus, there has been proposed one in which the reduction of power consumption is achieved by selecting alternately the time of waiting and that of reception at a given interval so as to perform the reception operation intermittently (refer to Japanese Patent Application Laid-Open No. 8-316965, Japanese Patent Application Laid-Open No. 10-190560, Japanese Patent Application Laid-Open No. 11-196027 and Japanese Patent Application Laid-Open No. 2001-109978, for example).
Such technique is also used in conventional wireless LAN communication systems; active scan is intermittently performed at the time of the automatic homing operation. However, in the case where active scan is simply performed intermittently at the same interval at the time of the automatic homing operation, even when there is no AP around the wireless LAN terminal apparatus, active scan will be repeated at the given interval, thus resulting in useless power consumption.